Focusing and stabilization are important issues in electronic imaging devices. Focusing is traditionally done by moving the whole lens back and forth from the sensor or some lens groups in lens systems. More recently a liquid lens focuser system was introduced.
For example, PHILIPS FLUID/FOCUS system mimics the action of the human eye using a fluid lens that alters its focal length by changing its shape. The new lens, which lends itself to high volume manufacturing, overcomes the fixed-focus disadvantages of many of today's low-cost imaging systems. The lens consists of two immiscible (non-mixing) fluids of different refractive index (optical properties), one an electrically conducting aqueous solution and the other an electrically non-conducting oil, contained in a short tube with transparent end caps. The internal surfaces of the tube wall and one of its end caps are coated with a hydrophobic (water-repellent) coating that causes the aqueous solution to form itself into a hemispherical mass at the opposite end of the tube, where it acts as a spherically curved lens. The shape of the lens is adjusted by applying an electric field across the hydrophobic coating such that it becomes less hydrophobic—a process called “electro-wetting” that results from an electrically induced change in surface-tension. As a result of this change in surface-tension, the aqueous solution begins to wet the sidewalls of the tube, altering the radius of curvature of the meniscus between the two fluids and hence the focal length of the lens. Thus it is possible to implement lenses that transition smoothly from being convergent to divergent and back again.
Image stabilization recently has become very popular in digital still and video cameras. Stabilization is also traditionally done by moving the lens, the lens group or the image sensor. But more recently a “Built-in Image Stabilizer” technology developed by CANON also delivers shake-free performance. Functional from the moment it is turned on, the system employs a VARI-ANGLE prism, dual transparent plates, independent vertical and horizontal sensors and a dedicated microprocessor to continuously adjust the prism to maintain a steady image. The VARI-ANGLE prism technique uses two prism elements and as these elements rotate in response to sensed motion, they can offset the light path and thus correct for the image shift.